It's an oft-repeated maxim that one of the reasons that Windows operating systems are plagued by so many viruses, worms, and security exploits is because they are so popular. Extrapolating on this, many have remarked that if Linux, MacOS, or other OSes become more popular, they will attract the attention of virus writers. That may be true, but the increased attention will not necessarily yield the same quantity of viruses and other exploits, says a Register article. Update: Rebuttal article.

Can you please explain how as you response looks like a semantic argument i.e. launching as opposed to executing.

I was commenting on the general "launching attachments" issue. The processes for non-executable attachments are the same.

Actual executable files are a specific example where Outlook & co. have greater functionality. The user still has to specifically authorise running the executable (in a dialog that defaults to "Save"). Some people might consider this a weakness, but I don't - I *like* having the option to run an executable without fiddling around with file permissions first.

Additionally, the difference between having to run a commandline tool and selecting an option in a dialog is largely semantic when talking about end users. If people are dumb enough to open things like "Anna nude", they're definitely silly enough to run "chmod a+x anna_nude" when an email tells them to.

The biggest security vulnerability - as is grudgingly admitted in the article - is social engineering. All current OSes have sufficient levels of programmatic security to provide a practically equivalent level of protection to the average end user. The problem is as soon as you start enforcing too much security programmatically, it encroaches on usability.

can you please name these "design" features, i'd like to make sure they don't affect me.

Unrestricted superuser.
The fact you have to be root to do anything even remotely low level.
Various kludges like privsep, sudo and suid binaries.

Basically, they all revolve around unix's primitive security model, which is barely more than a step away from that of DOS and classic MacOS.